The control modes for DTR are:
The Enable and Disable control modes of DTR affect DTR processing during a First Level Open. When these control modes are set through IOCtl ASYNC_SETDCBINFO, the value of the DTR signal can be modified immediately by the physical device driver. The action depends on the previous control mode of DTR and the current value of the DTR modem control signal. If the control mode of DTR is Input Handshaking, then the device driver controls the DTR signal, depending on how full the receive queue is. The bits that control these states of the device driver are in the device control block.
Initial Value